Neuroprotective

Ginkgo is the archetypal neuroprotective botanical and the most heavily human-trialled, but its effect is real-and-modest rather than powerful. The EGb 761 flavonol glycosides scavenge peroxyl/hydroxyl radicals and protect hippocampal neurons against beta-amyloid- and oxidative-stress-induced death in cell and animal models ^{9,10Reference 9Maitra I et al. · 1995In vitroPeroxyl radical scavenging activity of Ginkgo biloba extract EGb 761 — in vitro studyView study →Reference 10Bastianetto S et al. · 2000In vitroThe Ginkgo biloba extract (EGb 761) protects hippocampal neurons against cell death induced by beta-amyloid — in vitro studyView study →}, while the sesquiterpene bilobalide adds GABAergic and mitochondrial protection against ischaemic injury. Effect is tied to the standardised extract, and the honest ceiling is important: ginkgo does not prevent dementia — the ~3,000-patient GEM trial was null ^{11,12Reference 11DeKosky ST et al. · 2008RCTGinkgo biloba for prevention of dementia: a randomized controlled trial — randomised controlled trialView study →Reference 12Snitz BE et al. · 2009RCTGinkgo biloba for preventing cognitive decline in older adults: a randomized trial — randomised controlled trialView study →}.

Beyond enzyme inhibition, huperzine-A shows a consistent “non-cholinergic” protective profile: it antagonises the NMDA-receptor channel (anti-excitotoxic, relevant to seizure and nerve-agent injury) ^{2,3Reference 2Coleman BR et al. · 2008AnimalColeman BR, Ratcliffe RH, Oguntayo SA, et al. (2008). [+]-Huperzine A treatment protects against N-methyl-D-aspartate-induced seizure/status epilepticus in rats — rat in vivo. Chem Biol Interact. https://pubmed.ncbi.nlm.nih.gov/18588864/View study →Reference 3Gordon RK et al. · 2001In vitroThe NMDA receptor ion channel: a site for binding of huperzine A — in vitroView study →}, shifts amyloid precursor protein processing away from the amyloidogenic route (↓ BACE1, ↑ ADAM10, ↓ Aβ) while up-regulating nerve growth factor ^{4,5Reference 4Qian ZM · 2014ReviewHuperzine A: is it an effective disease-modifying drug for Alzheimer’s disease? — reviewView study →Reference 5Wongjaikam S et al. · 2024In vitroHuperzine A regulates the physiological homeostasis of amyloid precursor protein proteolysis and tau protein conformation — in vitro / in silicoView study →}, and dampens neuroinflammation via α7-nicotinic receptor activation and NF-κB/IL-6/TNF-α suppression ^{6,7Reference 6Su J et al. · 2024AnimalHuperzine A ameliorates sepsis-induced acute lung injury by suppressing inflammation and oxidative stress via α7 nicotinic acetylcholine receptor — mouse in vivoView study →Reference 7Shi J et al. · 2024In vitroHuperzine A protected against ferroptosis via activating PI3K/Akt signaling in lipopolysaccharide-induced acute lung injury — in vivo / in vitroView study →}. Real and mechanistically coherent, but a secondary story rather than the headline: every one of these findings is animal or cell-line only — none of the neuroprotection has been shown in humans, and it is the isolated alkaloid, not the herb. Parkinson’s protection is thinner still (mouse MPTP model only) ^{8Reference 8Guo X et al. · 2023AnimalHuperzine A injection ameliorates motor and cognitive abnormalities via regulating multiple pathways in a murine model of Parkinson’s disease — mouse in vivoView study →}.

Preclinical neuroprotection is a rich, active research area — especially for Alzheimer’s disease — but it stops at the animal boundary. Water extract improved memory and executive function in β-amyloid- overexpressing (5xFAD/Tg2576) mice, attenuated hippocampal mitochondrial dysfunction, reduced oxidative stress and activated NRF2 antioxidant genes ^{13,14Reference 13Matthews et al. · 2019AnimalCentella asiatica improves memory and promotes antioxidative NRF2 signaling in 5XFAD mice — animal modelView study →Reference 14Gray et al. · 2018AnimalCentella asiatica attenuates hippocampal mitochondrial dysfunction and improves memory and executive function in β-amyloid overexpressing mice — animal modelView study →}; asiatic acid is neuroprotective across cerebral-ischaemia, spinal-cord-injury, epilepsy and neurodegeneration models ^{15Reference 15Ding et al. · 2023ReviewNeuroprotective mechanisms of asiatic acid — reviewView study →}, and the 2012 review attributes brain effects to acetylcholinesterase and tyrosinase inhibition, dendritic arborisation and raised Na⁺/K⁺-ATPase ^{16Reference 16Orhan · 2012ReviewCentella asiatica (L.) Urban: From traditional medicine to modern medicine with neuroprotective potential — reviewView study →}. Capped at moderate: no human neuroprotection trial exists and human PK shows the parent glycosides are poorly absorbed, acting via acid metabolites ^{17,18Reference 17Songvut et al. · 2019Clinical trialSafety and pharmacokinetics of standardized extract of Centella asiatica (ECa 233) capsules in healthy volunteers — phase 1 clinical trialView study →Reference 18Songvut et al. · 2021Clinical trialPharmacokinetics and metabolomics of an orally modified formula of standardized Centella asiatica extract in healthy volunteers — clinical trialView study →}.

Several preclinical strands converge. In a β-amyloid (Aβ1-42) mouse Alzheimer model, 14 days of oral POEE prevented cognitive impairment while reducing amyloid deposits, astrogliosis and CA1 neuron loss ^{23Reference 23Figueiró et al. · 2011AnimalThe Amazonian herbal Marapuama attenuates cognitive impairment and neuroglial degeneration in a mouse Alzheimer model — animal studyView study →}; in rat hippocampal slices under oxygen-glucose deprivation (a stroke model) it preserved mitochondrial viability and blocked the free-radical rise ^{24Reference 24Siqueira et al. · 2004In vitroNeuroprotective effects of Ptychopetalum olacoides Bentham on oxygen and glucose deprivation-induced damage in rat hippocampal slices — in vitro studyView study →}. Most distinctively, Japanese groups isolated clerodane-type diterpenoids from the bark that potentiate nerve growth factor and drive neurite outgrowth in PC12 cells ^{25,26Reference 25Tang et al. · 2009In vitroNovel NGF-potentiating diterpenoids from a Brazilian medicinal plant, Ptychopetalum olacoides — in vitro studyView study →Reference 26Tang et al. · 2008In vitroClerodane diterpenoids with NGF-potentiating activity from Ptychopetalum olacoides — in vitro studyView study →} — a neuroregenerative signal separate from the AChE/antioxidant story. A genuine, mechanistically rich effect, but capped at moderate because there is no in-vivo confirmation the NGF diterpenoids act after oral dosing and no human data.

A single rigorous trial anchors this: an 18-month double-blind RCT (n=40 non-demented adults) of a bioavailable curcumin (Theracurmin, 90 mg twice daily) improved memory and attention versus placebo, with FDDNP-PET imaging suggesting reduced amyloid and tau accumulation in the amygdala and hypothalamus ^{30Reference 30Small GW et al. · 2018RCTMemory and Brain Amyloid and Tau Effects of a Bioavailable Form of Curcumin in Non-Demented Adults: a double-blind, placebo-controlled 18-month randomized controlled trialView study →}. Mechanistically plausible (anti-amyloid + anti-neuroinflammatory + Nrf2 antioxidant), but the potency ceiling is honest and low — one small trial of one proprietary bioavailable formulation, with exploratory imaging and no replication or dementia-incidence endpoint. Raw turmeric would not reach the plasma levels this used.

The neuroprotective tag rests almost entirely on reference ^{1Reference 1Wang et al. · 2010Composition, standardization and chemical profiling of Banisteriopsis caapi, a plant for the treatment of neurodegenerative disorders relevant to Parkinson’s diseaseView study →}, which profiles and standardises Banisteriopsis caapi explicitly as “a plant for the treatment of neurodegenerative disorders relevant to Parkinson’s disease” — a monoaminergic-preservation rationale flowing from the same β-carboline MAO inhibition ^{1Reference 1Wang et al. · 2010Composition, standardization and chemical profiling of Banisteriopsis caapi, a plant for the treatment of neurodegenerative disorders relevant to Parkinson’s diseaseView study →}. The monograph does not cite any neurogenesis, BDNF/neurotrophic, anti-excitotoxic or mitochondrial signal, so this is a framing-plus-mechanism inference, not a demonstrated neuroprotective effect; potency stays mild until the research section is built out.

The neuroprotective claim is the most preliminary lavender action. Lavender oil improved scopolamine-induced memory deficits and lowered oxidative-stress markers in rats ^{19Reference 19Xu et al. · 2016AnimalProtective effect of lavender oil on scopolamine-induced cognitive deficits in mice — animal modelView study →}, and related Lavandula extracts protected neurons in ischaemia and 6-OHDA models, with the effect attributed variously to whole oil, linalool, and minor constituents such as myrtenol. Single-model animal studies with no human counterpart — too early to call lavender neuroprotective in any human sense.

The neuroprotective tag is thin and entirely preclinical, tied specifically to black maca. Aqueous black-maca extract reversed ovariectomy-induced memory impairment in mice while lowering brain malondialdehyde and acetylcholinesterase (AChE) activity ^{20Reference 20Rubio et al. · 2011AnimalAqueous extract of black maca (Lepidium meyenii) on memory impairment induced by ovariectomy in mice — animal modelView study →}, and both aqueous and hydroalcoholic black-maca extracts corrected scopolamine-induced memory deficits, again via AChE inhibition ^{21Reference 21Rubio et al. · 2007AnimalAqueous and hydroalcoholic extracts of black maca (Lepidium meyenii) improve scopolamine-induced memory impairment in mice — animal modelView study →}. Reviews credit combined antioxidant + AChE-inhibitory activity and note black maca outperforms the other colours ^{22Reference 22Gonzales · 2012ReviewEthnobiology and ethnopharmacology of Lepidium meyenii (Maca), a plant from the Peruvian highlands — reviewView study →}. There are no human cognition trials and the mechanism is an induced-deficit rodent finding, so this is a mechanistically plausible but unproven action — and the yellow powder most people buy is not the form behind it.

The thinnest of the supported actions, and on a different preparation from the modern dermatologic extracts. Interest began with incidental cognitive reports in psoriasis patients on Anapsos, followed by a single small double-blind placebo-controlled pilot in 45 mild-to-moderate senile-dementia patients that examined cognition and cerebral haemodynamics ^{27Reference 27Álvarez et al. · 2000RCTDouble-blind, randomised, placebo-controlled pilot study with anapsos in senile dementia — randomisedView study →}; the only mechanism is a rat study in which anapsos modulated Cu-Zn superoxide dismutase in a beta-amyloid degeneration model ^{28Reference 28Fernández-Novoa et al. · 1997AnimalEffects of anapsos on Cu-Zn-superoxide dismutase activity in an animal model of neuronal degeneration — animalView study →}. Unreplicated since 2000, on the rhizome pharmaceutical rather than Fernblock — a preliminary signal, not an established action.

Mechanistically plausible but weakly substantiated for this herb as used. Green-tea extract and its catechins epicatechin and EGCG protected dopaminergic neurons in the 6-OHDA (Parkinson’s) model, attributed to an antioxidant and anti-inflammatory profile, with L-theanine possibly contributing ^{29Reference 29Bitu Pinto et al. · 2015Neuroprotective properties of the standardised extract from Camellia sinensis (green tea) in the 6-OHDA model of Parkinson’s disease — animalView study →}. This overlaps heavily with tea’s antioxidant and cognitive findings, but it is purely cell-culture and animal-model evidence — no human trials in Parkinson’s, Alzheimer’s or related disease — so potency stays mild.